Good Read: Designing Gestural Interfaces

(This post originally appeared on Hill Holliday Blog)

Designing Gestural Interfaces by Dan Saffer helps elaborate on this presentation “Tap is the New Click” at the 2009 IIT Design Conference. The book provides guidance on designing touch screens and motion-sensitive controllers, because these interfaces must be approached differently then keyboard-based applications.

Experiences with well-designed touch screens are derived from “direct manipulation”, a term first derived from Schneiderman’s seminal research (1983), which refers to the ability to have a direct line to manipulate the object right from the screen. To create good gestural interfaces, the objects must have levels of affordances, or properties that help indicate how the object is to be used.

According to Saffer, most gestural interfaces have three zones of engagement: attraction, observation, and interaction. With attraction, the user first spots the objects and is intrigued and interested in it, which typically happens from a distance. With observation, a person can see more details on the object. Observers can watch and observe others interacting with the object, which typically happens at mid-range. Interaction occurs from a close up range and this is when the user directly interacts with the object.

Designers must be able to display three-dimensional movement when designing gestural interfaces through effective prototypes. Prototypes can range from low fidelity to high fidelity prototypes. Saffer suggests the creation of scenarios, use cases, task flows, wireframes, storyboarding, and animations help to enhance the team’s understanding of the object. Echoing Dan Brown’s advice from Communicating Design: Developing Web Site Documentation for Design and Planning, documentation helps produce accountability and traceability of the iterations.

When designing gestures, it is important to keep in mind metaphor as you turn something abstract into gesture. It is best to play off of existing mental models when attempting to turn a concept from abstract to concrete. “The best metaphors are those that match the understood meaning of the gesture with the action being performed”. As touch screens and sensors become more prevalent in design, the metaphor of the desktop may need to be re-evaluated.

We must also keep in mind that the human body is constructed of muscles, joints, and tendons, which all impact the body’s motions of flexes and extensions. Saffer points out that “designers need to be aware of the limits of the human body when creating interfaces that are controlled by it”. The rule to design for should be as gestures get more complicated, less people can perform the gesture. Fitt’s Law should also be considered when designing for gestural interfaces: “a large target that is closer to the user is easier to point to than a smaller one farther away”.